On the Internet of Things, an article is connected to the Internet by using an information sensing device, to implement intelligent identification and management. The information sensing device used on the Internet of Things includes a radio frequency identification apparatus, an infrared sensor, a global positioning system, a laser scanner, and the like. By combining with the Internet, the foregoing device may implement remote sensing and control of all articles (for example, buildings, goods, climate, machines, and people), and is widely applied to multiple fields such as intelligent transportation, environmental protection, government work, public security, smart household, smart fire fighting, industry monitoring, elderly care, and personal health.
It is generally regarded that a first phase of the Internet of Things is machine to machine (M2M), that is, implementing free communication between machines. For a communications network (for example, a mobile cellular network), this communications service undertaken by the communications network is called MTC.
However, the large-scale development of M2M/MTC requires several necessary conditions, and one of the conditions is reduction of costs of a terminal (a communications module). Therefore, the Third Generation Partnership Project (3GPP) puts forward a low-cost UE, which only supports relatively small system bandwidth, for example, only supports channel bandwidth of 1.4 megahertz (MHz) or 3 MHz, or only supports transmission bandwidth of six resource blocks (RB) or 15 resource blocks. Because only relatively small system bandwidth needs to be considered during product design and it is not required to consider a problem of a Long Term Evolution (LTE) system whose access channel bandwidth is 20 MHz or transmission bandwidth is 100 resource blocks, costs of the terminal can be saved greatly. In addition, if the foregoing UE only supporting small bandwidth is applied to an LTE system, it is helpful in migrating an existing M2M application deployed on a Global System for Mobile Communications (GSM)/General Packet Radio Service (GPRS) system/network to the LTE system, so that an operator can re-develop a frequency band of the existing GSM or GPRS system.
Under a background of a communications service of MTC, before sending downlink MTC data to a UE, a base station needs to perform MTC resource configuration for the UE in downlink system bandwidth of the base station. The MTC resource configuration is used to reserve a resource for the UE in the downlink system bandwidth, so as to send the downlink MTC data to the UE by using the reserved resource. Different base stations may configure a resource reserved for a UE in different locations of downlink system bandwidth. This flexible MTC resource configuration manner is helpful in coordinating interference between cells and extending an MTC capacity.
In the foregoing MTC resource configuration manner, if a small-bandwidth UE uses narrow band radio frequency reception, design may be greatly simplified and costs of the UE may be reduced. As shown in FIG. 1, a horizontal axis represents downlink system bandwidth of a base station, and a dashed area is a resource that is reserved by a base station in the downlink system bandwidth of the base station for a UE using narrow band radio frequency reception. In an original common reception manner of the UE, a local oscillator frequency of a receiver of the UE is set to be at a center of the entire downlink system bandwidth; in a data reception process of the receiver of the UE, a direct current component (called a system direct current) is easily generated in a location of the local oscillator frequency of the receiver, thereby affecting reception of downlink data. Therefore, when the base station transmits a downlink signal, a direct current subcarrier is sent in a location in which f0 shown in FIG. 1 is located. The direct current subcarrier is not used to transmit data, which ensures correctness of downlink data reception performed by the UE. However, when the UE uses narrow band radio frequency reception, the local oscillator frequency of the receiver of the UE is set to be in a central location of the resource that is reserved by the base station for the UE, that is, a location in which f1 in FIG. 1 is located. Therefore, the direct current component generated by the receiver of the UE moves to the location in which f1 is located (called an MTC direct current). Obviously, the location in which the MTC direct current is located does not overlap the location in which the original system direct current is located, and a subcarrier in the location in which the MTC direct current is located is still used to transmit the downlink data. Therefore, generation of an MTC direct current affects accurate reception of data on a subcarrier nearby the MTC direct current.